PubMed Health⌕ Search

Biomedical subjects

G Scarlatti

Publications and source records attributed to G Scarlatti.

At least 19 recordsLinked to original sources
PubMed2003

Mother-to-child transmission of HIV: developing integration of healthcare programmes with clinical, social and basic research studies. Report of the International Workshop held at Chobe Marina Lodge, Kasane, Botswana, 21-25 January 2003.

Considerable efforts are still needed in the public health sector, as well as in clinical, social and basic research, to improve programmes for HIV-1 MTCT (mother-to-child transmission) prevention and care. Advantage should be taken of the remarkable amount of expertise and resources that have accumulated over the past few years to accelerate the process of integration. Future initiatives should include integrating specialists and people with diverse backgrounds and targeting their scientific and programmatic ideas to address real-world problems in the area of MTCT of HIV-1.

Female↗
PubMed2001

Length variation of glycoprotein 120 V2 region in relation to biological phenotypes and coreceptor usage of primary HIV type 1 isolates.

Conflicting data have been published concerning the correlation between the length of the second variable region (V2) in the HIV-1 envelope and the biological phenotype of the virus. Here the V2 region length of primary HIV-1 isolates was compared with biological phenotype and coreceptor usage. The V2 region variation was determined by DNA fragment length analysis, virus biological phenotype by the MT-2 cell assay, and coreceptor usage by infection of U87.CD4 cells expressing CCR3, CCR5, or CXCR4. Ninety-three primary virus isolates from 40 patients were analyzed. This panel of viruses included sequential isolates obtained from patients who progressed to AIDS with or without a virus phenotypic switch. We found that NSI MT-2-negative isolates had significantly shorter V2 regions than SI MT-2-positive isolates. However, when V2 region lengths of viruses were analyzed in more detail, we observed that NSI isolates obtained from patients shortly before the phenotypic switch had V2 region lengths similar to those of SI isolates. V2 regions of NSI isolates obtained from patients who progressed to AIDS without a virus phenotypic switch had, in contrast, shorter V2 region than isolates obtained just before virus phenotypic switch. Coreceptor analysis revealed that CCR5-using (R5) isolates generally had shorter V2 regions than virus isolates with the ability to enter CXCR4-expressing cells. Moreover, no significant difference in V2 region length was observed between monotropic SI isolates, that is, X4 isolates, and multitropic SI isolates, that is, R3R5X4 or R5X4 isolates. Thus, we conclude that R5 NSI isolates obtained from patients with stable virus phenotype through the whole disease course display shorter V2 regions than isolates obtained from patients at switch of virus phenotype, suggesting that V2 region length may influence virus coreceptor usage.

Adult↗
PubMed2001

HIV type 1 chemokine receptor usage in mother-to-child transmission.

To investigate the role of the HIV-1 phenotype in mother-to-child HIV-1 transmission, we evaluated coreceptor usage and replication kinetics in chemokine receptor-expressing U87MG.CD4 cells of primary isolates from 32 HIV-1-infected mothers of Italian origin, none under preventive antiretroviral therapy, and from their infected infants. Five of 15 mothers of infected children and 2 of 17 mothers of uninfected children harbored viruses able to use CXCR4 as coreceptor. However, all isolates used CCR5, alone or in association with CXCR4. The replicative capacity in coreceptor-expressing cells of the viral isolates did not differ between the two groups of mothers. All mothers with an R5 virus transmitted a virus with the same coreceptor usage, whereas those four with a multitropic virus transmitted such a virus in one case. Although the presence of a mixed viral population was documented in the mothers, we did not observe transmission solely of X4 viruses. Interestingly, the only child infected with a multitropic virus carried a defective CCR5 allele. Analysis of the env V3 region of the provirus from this child revealed infection with multiple viral variants with a predominance of R5-type over X4-type sequences. These findings show that CCR5 usage of a viral isolate is not a discriminating risk factor for vertical transmission. Furthermore, X4 viruses can be transmitted to the newborn, although less frequently. In particular, we document the transmission of multiple viral variants with different coreceptor usage in a Delta32 CCR5 heterozygous child, and demonstrate that the heterozygous genotype per se does not contribute to the restriction of R5-type virus spread.

Amino Acid Sequence↗
PubMed2001

Follow-up of vertically HIV-1-infected long-surviving children.

This study describes the clinical, immunologic, and virological characteristics of 30 vertically human immunodeficiency virus type 1 (HIV-1)-infected children older than 8 years of age (long-survivors) before the introduction of protease inhibitors therapy. All of them were followed from birth. At the age of 8 years, 7 children presented no HIV-1-associated signs or only mild ones and only 5 had severe clinical manifestations (acquired immune deficiency virus [AIDS]). The remaining 18 children presented moderate signs with some immunodeficiency. The follow-up from 8 years of age (3.5 years on the average) showed that 6 children remained asymptomatic and were therefore defined as long-survivors nonprogressors (average, 13 years) and only 4 children developed AIDS. Progressive encephalopathy was the most striking clinical manifestation at follow-up and occurred in 6 children (always after immunodeficiency) with a polymorphic picture combining eye movement alterations, pyramidal signs and symptoms and mental deterioration. The majority of our long-survivors carried a virus with nonsyncytia-inducing phenotype, thus confirming its association with long survival. A switch to syncytia-inducing phenotype was observed only in 2 cases during the follow-up, but their clinical status did not change at follow-up.

Adolescent↗
PubMed2001

Determination of coreceptor usage of human immunodeficiency virus type 1 from patient plasma samples by using a recombinant phenotypic assay.

We developed a recombinant virus technique to determine the coreceptor usage of human immunodeficiency virus type 1 (HIV-1) from plasma samples, the source expected to represent the most actively replicating virus population in infected subjects. This method is not subject to selective bias associated with virus isolation in culture, a step required for conventional tropism determination procedures. The addition of a simple subcloning step allowed semiquantitative evaluation of virus populations with a different coreceptor (CCR5 or CXCR4) usage specificity present in each plasma sample. This procedure detected mixtures of CCR5- and CXCR4-exclusive virus populations as well as dualtropic viral variants, in variable proportions. Sequence analysis of dualtropic clones indicated that changes in the V3 loop are necessary for the use of CXCR4 as a coreceptor, but the overall context of the V1-V3 region is important to preserve the capacity to use CCR5. This convenient technique can greatly assist the study of virus evolution and compartmentalization in infected individuals.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Cell-to-cell contact results in a selective translocation of maternal human immunodeficiency virus type 1 quasispecies across a trophoblastic barrier by both transcytosis and infection.

Mother-to-child transmission can occur in utero, mainly intrapartum and postpartum in case of breastfeeding. In utero transmission is highly restricted and results in selection of viral variant from the mother to the child. We have developed an in vitro system that mimics the interaction between viruses, infected cells present in maternal blood, and the trophoblast, the first barrier protecting the fetus. Trophoblastic BeWo cells were grown as a tight polarized monolayer in a two-chamber system. Cell-free virions applied to the apical pole neither crossed the barrier nor productively infected BeWo cells. In contrast, apical contact with human immunodeficiency virus (HIV)-infected peripheral blood mononuclear cells (PBMCs) resulted in transcytosis of infectious virus across the trophoblastic monolayer and in productive infection correlating with the fusion of HIV-infected PBMCs with trophoblasts. We showed that viral variants are selected during these two steps and that in one case of in utero transmission, the predominant maternal viral variant characterized after transcytosis was phylogenetically indistinguishable from the predominant child's virus. Hence, the first steps of transmission of HIV-1 in utero appear to involve the interaction between HIV type 1-infected cells and the trophoblastic layer, resulting in the passage of infectious HIV by transcytosis and by fusion/infection, both leading to a selection of virus quasispecies.

Cell Communication↗
PubMed2000

Polymorphisms in the MBL2 promoter correlated with risk of HIV-1 vertical transmission and AIDS progression.

We investigated the polymorphisms of the promoter region of the MBL2 gene, which codifies for the Mannose-binding protein (MBP). The study population included 90 children with vertically acquired HIV-infection, further divided on the basis of the disease rate, 27 HIV exposed-uninfected children, and 74 healthy control subjects matched for ethnic origin to evaluate the MBP involvement in the risk of HIV-1 infection and to assess the role of the MBP promoter in AIDS progression. A region of 380 bp in the promoter of the MBL2 gene was analysed by PCR and direct sequencing of both DNA strands. We found that the polymorphism at position -550 influences the risk of HIV-infection and AIDS progression. Also a 6 bp deletion at position -328 was correlated with HIV-1 infection. This study indicates that the promoter of the MBL2 gene influences vertical transmission of HIV and the course of perinatal infection.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Prognostic value of a CCR5 defective allele in pediatric HIV-1 infection.

BACKGROUND: A deletion of 32 base pairs in the CCR5 gene (delta32 CCR5) has been linked to resistance to HIV-1 infection in exposed adults and to the delay of disease progression in infected adults. MATERIALS AND METHODS: To determine the role of delta32 CCR5 in disease progression of HIV-1 infected children born to seropositive mothers, we studied a polymerase chain reaction in 301 HIV-1 infected, 262 HIV-1 exposed-uninfected and 47 HIV-1 unexposed-uninfected children of Spanish and Italian origin. Infected children were further divided into two groups according to their rate of HIV-1 disease progression: rapid progressors who developed severe clinical and/or immunological conditions within the second year of life, and delayed progressors with any other evolution of disease. Among the latter were the long-term, non-progressors (LTNP) who presented with mild or no symptoms of HIV-1 infection above 8 years of age. Viral phenotype was studied for 45 delayed progressors. RESULTS: No correlation was found between delta32 CCR5 and mother-to-child transmission of HIV-1. However, the frequency of the deletion was substantially higher in LTNP, compared with delayed (p = 0.019) and rapid progressors (p = 0.0003). In children carrying the delta32 CCRS mutation, the presence of MT-2 tropic virus isolate was associated with a severe immune suppression (p = 0.028); whereas, the presence of MT-2 negative viruses correlated with LTNP (p = 0.010). CONCLUSIONS: Given the rapidity and simplicity of the assay, the delta32 CCR5 mutation may be a useful predictive marker to identify children with delayed disease progression who, consequently, may not require immediate antiretroviral treatment.

Adolescent↗
PubMed1999

Nonproductive human immunodeficiency virus type 1 infection of human fetal astrocytes: independence from CD4 and major chemokine receptors.

Human immunodeficiency virus type 1 (HIV-1) infection of the brain is associated with neurological manifestations both in adults and in children. The primary target for HIV-1 infection in the brain is the microglia, but astrocytes can also be infected. We tested 26 primary HIV-1 isolates for their capacity to infect human fetal astrocytes in culture. Eight of these isolates, independent of their biological phenotype and chemokine receptor usage, were able to infect astrocytes. Although no sustained viral replication could be demonstrated, the virus was recovered by coculture with receptive cells such as macrophages or on stimulation with interleukin-1beta. To gain knowledge into the molecular events that regulate attachment and penetration of HIV-1 in astrocytes, we investigated the expression of several chemokine receptors. Fluorocytometry and calcium-mobilization assay did not provide evidence of expression of any of the major HIV-1 coreceptors, including CXCR4, CCR5, CCR3, and CCR2b, as well as the CD4 molecule on the cell surface of human fetal astrocytes. However, mRNA transcripts for CXCR4, CCR5, Bonzo/STRL33/TYMSTR, and APJ were detected by RT-PCR. Furthermore, infection of astrocytes by HIV-1 isolates with different chemokine receptor usage was not inhibited by the chemokines SDF-1beta, RANTES, MIP-1beta, or MCP-1 or by antibodies directed against the third variable region or the CD4 binding site of gp120. These data show that astrocytes can be infected by primary HIV-1 isolates via a mechanism independent of CD4 or major chemokine receptors. Furthermore, astrocytes are potential carriers of latent HIV-1 and on activation may be implicated in spreading the infection to other neighbouring cells, such as microglia or macrophages.

Adult↗
PubMed1999

An unusual HIV type 1 env sequence embedded in a mosaic virus from Cameroon: identification of a new env clade. European Network on the study of in utero transmission of HIV-1.

An atypical HIV-1 strain (CAM001) was identified in a pregnant Cameroonian woman in 1995. HMA subtyping of the env region was unsuccessful, and sequence analyses were performed. Unique sequence motifs were found at the V3 tip (GAGRALHA and GAGRAWIHA), and phylogenetic studies showed that the env C2-V5 sequence branched within group M but remained distinct from all known HIV-1 subtypes, while p17 gag branched with the subtype F sequences. Four other HIV group M viruses, undetermined by HMA, of African origin were found to cluster with CAM001 in the C2-V5 sequences. With the BLAST method, we found in databases three strains whose V3 sequences also clustered with CAM001. These unusual env sequences from eight HIV-1 strains derived from Cameroon formed a separate cluster in HIV-1 group M, which we designated k.

Amino Acid Sequence↗
PubMed1999

Enhanced HIV infectivity and changes in GP120 conformation associated with viral incorporation of human leucocyte antigen class I molecules.

BACKGROUND: Assembly of human immunodeficiency virus type 1 (HIV-1) occurs at the level of the plasma membrane of the host cell. During this process HIV incorporates significant quantities of cell surface-derived molecules into its lipid bilayer including human leucocyte antigen (HLA) class I and II, intercellular adhesion molecule-1 and lymphocyte function antigen-1. Several studies indicate that virion-bound host-cell-derived molecules are functional and affect the biological properties of HIV-1. Virion-associated HLA class II and intercellular adhesion molecule-1 enhance the infectivity of T-cell line-adapted (TCLA) viruses. No role for virion-associated HLA class I molecules has yet been identified. OBJECTIVE: To investigate the role of HLA class I molecules in HIV replication and infectivity. METHODS: HLA class I negative human cells lines transfected with the HLA Cw4 gene were infected with different TCLA viruses as well as primary X4 isolates. The infectivity of HLA Cw4 positive and negative viruses was determined on indicator cell lines and on phytohaemagglutinin-activated peripheral blood mononuclear cells. An entry polymerase chain reaction assay was used to determine differences in entry-competence of Cw4 positive and negative viruses. The expression of selected gp120 epitopes on native Env molecules derived from Cw4 positive and negative viruses was determined by a monoclonal antibody-based enzyme-linked immunosorbent assay. Immunoprecipitation experiments were performed to investigate the presence of gp120/HLA Cw4 complexes. Neutralization assays determined the differences in susceptibility to neutralization between HLA Cw4 negative and positive viruses. RESULTS AND CONCLUSIONS: The infectivity of primary HIV-1 X4 isolates and of TCLA viruses is increased upon viral incorporation of HLA Cw4 molecules. This effect is associated with changes in viral envelope proteins conformation including an enhanced expression of the V3 loop of gp120, and of epitopes that are exposed upon CD4 binding. The gp120 conformational changes are consistent with the formation of a multimolecular complex between HLA class I and gp120/160. HLA Cw4 incorporation is also associated to a lower susceptibility to antibody neutralization. These findings have important implications for understanding the immune response to cryptic and conformational epitopes of the viral envelope.

Cell Line↗
PubMed1999

Selection of maternal human immunodeficiency virus type 1 variants in human placenta. European Network for In Utero Transmission of HIV-1.

To determine the mechanisms by which human immunodeficiency virus type 1 (HIV-1) crosses the placenta into the fetal blood, 12 matched samples of serial maternal blood, term placentas, and infant blood obtained from a cohort of pregnant women in Cameroon identified as predominantly infected by subtype A viruses were studied. HIV-1 env sequences were detected by polymerase chain reaction (PCR) in both chorionic villi and enriched trophoblastic cells of all 12 placentas but at variable rates of detection. Heteroduplex mobility assay analysis showed the presence of multiple HIV-1 env quasispecies in sequential maternal peripheral blood mononuclear cell samples, but only a small number of env variants were found in chorionic villi and enriched trophoblastic cells. These data indicate that HIV-1 env sequences are always present in term placentas of seropositive women, contrasting with the low frequency at which infection is diagnosed by PCR in neonates with tat, gag, and env primers. Maternal HIV-1 variants appear to undergo a strong negative selection by different cell populations within the placental villi.

Base Sequence↗
PubMed1998

CXCR4 is a functional coreceptor for infection of human macrophages by CXCR4-dependent primary HIV-1 isolates.

The identification of HIV-1 coreceptors has provided a molecular basis for the tropism of different HIV-1 strains. CXC chemokine receptor-4 (CXCR4) mediates the entry of both primary and T cell line-adapted (TCLA) syncytia-inducing strains. Although macrophages (M phi) express CXCR4, this coreceptor is assumed to be nonfunctional for HIV-1 infection. We addressed this apparent paradox by infecting human monocyte-derived M phi with primary and TCLA isolates that were rigorously characterized for coreceptor usage and by adding the natural CXCR4 ligand, stem cell differentiation factor-1, to specifically block CXCR4-mediated entry. Our results show that primary HIV-1 isolates that selectively use CXCR4 productively infected both normal and C-C chemokine receptor-5-null M phi. By contrast, M phi supported the entry of CXCR4-dependent TCLA strains with variable efficiency but were not productively infected. Thus, the tropism of HIV isolates results from complex virus/host cell interactions both at the entry and postentry levels.

Anti-HIV Agents↗
PubMed1997

Correlation between HIV sequence evolution, specific immune response and clinical outcome in vertically infected infants.

OBJECTIVE: To evaluate sequence evolution in relation to different rates of disease progression in infants infected with HIV-1. DESIGN: Variability in the gp120 V3 region was analysed in HIV-1-infected children with different clinical courses, slow progression (n = 2) versus progressive disease (n = 3). METHODS: Cloning and sequencing of virus-derived DNA from uncultured peripheral blood mononuclear cells was performed at two to three timepoints from birth and up to the fifth year of life. Sequence variability was estimated by calculating the genetic distance and the proportion and ratio of synonymous and non-synonymous nucleotide substitutions over time. RESULTS: Genetic distances were significantly shorter in children with fast progression to disease, a predominance of synonymous nucleotide substitutions also being detected at later timepoints. Conversely, a preferential accumulation of non-synonymous nucleotide substitutions was apparent in children with slow disease progression. Furthermore, a positive correlation between a decreased ratio of synonymous/non-synonymous nucleotide substitutions and the ability of children's sera to react with synthetic peptides representing the autologous virus sequence was determined. CONCLUSION: Data suggest that an antigenically more diverse virus population emerges in infected children with slower progression to disease as a result of a stronger immune pressure.

Amino Acid Sequence↗
PubMed1997

Antigen-driven C-C chemokine-mediated HIV-1 suppression by CD4(+) T cells from exposed uninfected individuals expressing the wild-type CCR-5 allele.

Despite repeated exposure to HIV-1, certain individuals remain persistently uninfected. Such exposed uninfected (EU) people show evidence of HIV-1-specific T cell immunity and, in rare cases, selective resistance to infection by macrophage-tropic strains of HIV-1. The latter has been associated with a 32-base pair deletion in the C-C chemokine receptor gene CCR-5, the major coreceptor of macrophage-tropic strains of HIV-1. We have undertaken an analysis of the HIV-specific T cell responses in 12 EU individuals who were either homozygous for the wild-type CCR-5 allele or heterozygous for the deletion allele (CCR-5Delta32). We have found evidence of an oligoclonal T cell response mediated by helper T cells specific for a conserved region of the HIV-1 envelope. These cells produce very high levels of C-C chemokines when stimulated by the specific antigen and suppress selectively the replication of macrophage-tropic, but not T cell-tropic, strains of HIV-1. These chemokine-producing helper cells may be part of a protective immune response that could be potentially exploited for vaccine development.

Alleles↗
PubMed1997

C-C chemokines released by lipopolysaccharide (LPS)-stimulated human macrophages suppress HIV-1 infection in both macrophages and T cells.

Human immunodeficiency virus-1 (HIV-1) expression in monocyte-derived macrophages (MDM) infected in vitro is known to be inhibited by lipopolysaccharide (LPS). However, the mechanisms are incompletely understood. We show here that HIV-1 suppression is mediated by soluble factors released by MDM stimulated with physiologically significant concentrations of LPS. LPS-conditioned supernatants from MDM inhibited HIV-1 replication in both MDM and T cells. Depletion of C-C chemokines (RANTES, MIP-1 alpha, and MIP-1 beta) neutralized the ability of LPS-conditioned supernatants to inhibit HIV-1 replication in MDM. A combination of recombinant C-C chemokines blocked HIV-1 infection as effectively as LPS. Here, we report an inhibitory effect of C-C chemokines on HIV replication in primary macrophages. Our results raise the possibility that monocytes may play a dual role in HIV infection: while representing a reservoir for the virus, they may contribute to the containment of the infection by releasing factors that suppress HIV replication not only in monocytes but also in T lymphocytes.

Cells, Cultured↗